The goal is to prepare tenfold redundant Bacterial Artificial Chromosomes (BAG) libraries for species selected by an NIH advisory committee and to disseminate the libraries in accordance with NIH policy. The libraries will be tailored to the scientific community's interest in comparative genomics and be used in support of whole-genome sequencing projects. The project is a continuation of an earlier cooperative agreement between the NIH and the Children's Hospital Oakland Research Institute. The application has four components relevant to preparing (BACs): 1) Library preparation, 2) Clone Arraying & Library Duplication, 3) Characterization, and 4) Research & Development to improve the process efficiency and BAG library quality. During the first year, four BAG libraries will be prepared for genomes having a typical mammalian genome size. This corresponds with an "800,000 BAG clone" preparation capacity. During years two and three of the program, improvements in BAG construction methods may result in slight increases in throughput. The small size of the continuation program does not offer opportunities for "economy of scale" improvements. The new libraries will complement the extensive repertoire of BAG clone collections already available for comparative genome analysis. The new clone collections will be analyzed by a standardized set of tests, including screening with a set of genomic markers, limited BAC-end sequencing and insert size determination. Once the libraries pass the quality controls, the new resources will be made available in a format consistent with major applications. To facilitate access to the BAG libraries, a screening service based on cost recovery by user fees has been established. It is expected that the new BAG resources will continue to contribute to better understanding of human gene function and evolution through comparison of human genes with a growing spectrum of animal species. BAG clones will also increasingly be used as tools to create animal models for human diseases. Widespread dissemination of the clones is an essential component of the project. User fees for most libraries cannot cover the costs of maintenance. Hence, mimimal funding is requested in support of the maintenance of the new libraries and those generated under the previous program initiative. Information about libraries available through the website for BACPAC Resources (http://bacpac.chori.org).